#include<stdio.h>
int main(void){
    int score;
    scanf("%d",&score);
    switch(score/10){
        case 10:;
        case 9: printf("A");break;
        case 8: printf("B");break;
        case 7: printf("C");break;
        case 6: printf("D");break;
        default: printf("E");break;
    }
    return 0;
}